1. Field of the Invention
The present invention relates generally to improved, sealed containers enclosing medical and/or bio-medical articles for gas sterilization after packaging and storing such articles in sterile condition, and particularly to containers of the described class having readily removable covers.
2. Background of the Invention
There are presently in use various forms of bacteria-impermeable containers for storing in sterile condition articles of a medical or bio-medical nature. One kind of container comprises a relatively rigid tray sealed by a removable cover a portion or all of which is made of a material highly permeable to sterilizing vapors such as ethylene oxide or steam thereby permitting sterilization of the contents after the container has been sealed. The sterile article is removed from the tray by peeling back the cover which is typically heat sealed to the rim of the tray.
The covers of known containers of this kind have various disadvantages. For example, some have small windows or ports covered by a patch of vapor-permeable material. The manufacture of such covers requires exact registration between the port, patch and the mechanism that seals the patch to the cover thereby necessitating the use of additional apparatus which substantially increases the cost of the final product. Moreover, because of the small area of the port, the breathability is often insufficient to permit an adequate rate of penetration and removal of the sterilizing vapor without risk of rupturing the container.
Furthermore, various cover materials presently in use are opaque thereby making impossible the verification of the contents of the container short of removal of the cover. Such verification prior to removal of the cover is important, for example, where the contents of the container comprise a specific set of surgical instruments for use in connection with a particular surgical procedure.
One cover material in wide use is "Tyvek", a spun polyolefin of the du Pont Company. "Tyvek", however, is not only opaque but is very expensive and must be coated with bonding agents such as heat sealable lacquers or resins in order to seal it to the tray. But such coatings reduce the breathability of "Tyvek", sometimes to a point where the rate of transfer of the sterilization vapor is insufficient. Efforts have been made to coat such covers with bonding agents or heat seal layers in only those places where a seal is to be effected so as not to limit breathability. However, this raises problems of registration. For example, peripheral coatings of bonding agents must be properly positioned with respect to both the printing on the cover and the tray to which the cover is to be attached. Such localized coating can, of course, be accomplished but it raises manufacturing difficulty and costs substantially.
Lastly, the covers of certain containers often tear when an attempt is made to remove them. This results in non-sterile parts of the cover or debris from the torn portions of the cover coming in contact with the contents of the container. It is desirable therefore that the cover be removable from the tray as a single piece without tearing and that the separation of the cover and tray not produce any loose fibers or debris.